Many Micro-electromechanical systems (MEMS) devices are typically manufactured using a silicon wafer having a 5-35 μm thick, highly boron-doped (p++), epitaxial layer deposited on at least one of its sides. Structures (e.g. accelerometers) are etched in the epitaxial layer employing masks and either dry or non-selective wet etch techniques. The un-doped (or lightly doped) portion of the wafer (handle layer) is dissolved in a selective chemical etchant that etches the un-doped or lightly doped silicon 100-1000 times faster than it etches the p++ doped silicon, leaving behind the structures in the p++ doped epitaxial layer. For many of these MEMS devices, the epitaxial layer thickness is critical to the performance of the etched structures. There is, however, no nondestructive way to measure this thickness.